The present invention relates to a printing device for printing predetermined data on wrapping paper in the process of manufacturing cigarettes by continuously wrapping shredded tobacco in the wrapping paper.
A printing device of this kind is disclosed, for example, in Japanese Patent Unexamined Publication No. Sho 56-164867. The device disclosed there comprises an ink container holding ink, an ink nozzle connected with the ink container by a supply passage, and a gear pump inserted in the supply passage. When the gear pump is actuated, the gear pump supplies the ink held in the ink container through the supply passage to the ink nozzle.
In the case of the above printing device, in order to keep the clearness of data printed on the wrapping paper, that is, the printing density substantially constant, the rate of supplying ink to the ink nozzle needs to be regulated depending on the printing density. The rate of supplying ink is regulated by controlling the actuation of the gear pump, but due to the structure of the gear pump, the flow of the ink delivered from the gear pump inevitably shows pulsation. Therefore, in the above printing device, the rate of supplying ink cannot be regulated precisely.
When cigarettes of another brand are to be manufactured, for which data needs to be printed on the wrapping paper in another color, the ink container needs to be replaced with another one and the supply passage connecting the ink container and the ink nozzle needs to be cleaned.
In the case of the printing device using the gear pump, the supply passage is long and not easy to clean. In addition, the gear pump has a complicated internal structure, therefore, it is not easy to clean the inside of the gear pump.
An object of the present invention is to provide a printing device for printing on wrapping paper that can control the rate of supplying ink easily with a simple structure, and can be prepared easily when printing color is to be changed.
The printing device that attains the above object comprises a printing roller train for printing predetermined data on wrapping paper, having a pair of inlet rollers at a starting end thereof and a printing roller at a terminal end thereof; an ink nozzle for ejecting ink between the pair of inlet rollers; and an ink supply unit for supplying ink to the ink nozzle. Here, the ink supply unit includes an ink cartridge having an ink chamber defined by a movable wall therein and filled with ink, and an ink discharge port, an ink supply passage connecting the ink discharge port of the ink cartridge and the ink nozzle, a linear actuator for pushing the movable wall into the ink cartridge, and control means for controlling action of the linear actuator.
In the above printing device, as the movable wall in the ink cartridge is pushed in by the linear actuator, the ink in the ink cartridge is delivered from the ink discharge port through the ink supply passage to the ink nozzle and ejected from the ink nozzle between the pair of inlet rollers.
The ink is thus ejected from the ink nozzle by the linear actuator pushing the movable wall in. Therefore, the rate of ejecting ink can be controlled precisely by the moving speed of the movable wall. In addition, the rate of ejecting ink from the ink nozzle is free of pulsation. Further, the ink discharge port of the ink cartridge and the ink nozzle are simply connected by the only ink supply passage. Therefore, the ink supply passage can be cleaned easily.
Preferably, the ink supply unit further includes a cartridge holder for detachably housing the ink cartridge therein, and the cartridge holder is located near the ink nozzle. In this case, the ink supply passage connecting the ink cartridge and the ink nozzle can be short.
The cartridge holder may have a nozzle mount for fitting the ink nozzle thereto, at the outside thereof. In this case, the ink supply passage can be further shorter, therefore, further easier to clean.
The nozzle mount may have a nozzle connecting opening adapted to connect with the inside of the ink nozzle. In this case, the ink supply passage can be defined in the cartridge holder.
When the ink supply passage is defined in the cartridge holder, an additional member such as a hose or tube is not needed to connect the ink cartridge and the ink nozzle. The passage for supplying ink from the ink cartridge to the ink nozzle can be provided easily, and the ink supply unit can be a simpler structure.
Specifically, the cartridge holder includes a cylinder that opens at both ends thereof and has a containing chamber adapted to contain the ink cartridge, and an end wall for closing one of the open ends of the cylinder. The end wall has a cartridge connecting hole adapted to be detachably engaged with the ink discharge port of the ink cartridge when the ink cartridge is housed in the cylinder, and the connecting hole provides an end of the ink supply passage. According to this structure, the ink cartridge can connect with the ink passage at the same time the ink cartridge is housed in the cartridge holder.
It is preferably that the end wall of the cartridge holder is detachably attached to the cylinder. In this case, the part of the ink supply passage extending in the end wall can be cleaned in a state that the end wall has been detached from the cylinder. Here, it is more preferably if the cartridge holder is arranged so as to extend along the axes of the inlet rollers and the nozzle mount is provided at the outer peripheral surface of the cylinder of the cartridge holder. In this case, through the open end of the cylinder from which the end wall has been detached, the ink cartridge can be loaded into or unloaded from the cartridge holder without being hindered by the inlet rollers.
The linear actuator is supported at the other open end of the cylinder and has a push rod projecting into the cylinder. The push rod is adapted to push the movable wall when it is expanded and to be separated from the movable wall when it is contracted. According to this structure, the ink cartridge can be unloaded from the cartridge holder making use of the push rod being expanded.
It is preferably that the ink nozzle is detachably attached to the nozzle mount. In this case, the inside of the ink nozzle can be cleaned, separately. The ink nozzle may comprise a separable pair of nozzle halves, and a nozzle passage defined between the nozzle halves to extend from the nozzle connecting opening to the tip end of the ink nozzle. In this case, the inside of the ink nozzle can be cleaned more easily.
The control means comprises a sensor for detecting the density of data printed on the wrapping paper and sending out a corresponding detection signal, and a regulating means for regulating the speed of the movable wall being pushed in by the linear actuator, based on the detection signal from the sensor.
The range of further application of the present invention will become more apparent from the detailed description below. The detailed description below, which will include description of specific examples, relates to a desirable embodiment of the present invention, but various modifications and improvements that can be made in accordance with the concept of the present invention within the range thereof would be apparent to a person skilled in this technical field.